This invention relates generally to the field of work zone enclosures for laser beam and for shielding of the environmental areas surrounding laser work zones.
The invention relates in particular to work zones where a wieldable laser gun or focusing apparatus is moved through multispatial orientations when performing operations on a workpiece.
It has been known to use low power laser beams for performing a variety of functions such as aligning machines, wherein a red visible laser beam might be employed to effect the alignment. Such low power laser beams generally present no problem to surrounding areas and personnel. Recently, however, it has become useful to employ what are known as "power lasers" to effect material cutting and welding operations. What is meant by power lasers are those typically, in the neighborhood of lkw, more or less, which have a light beam capable of burning through material if left on the target spot and, similarly, which are capable of inflicting injury on personnel because of the level of energy employed.
Many types of laser generating media may be employed to effect power lasing, for example, solid lasers (e.g. ruby crystal), and gas lasers (e.g., carbon dioxide) to name several.
Conventional laser cutting and welding apparatus generally employ a fixed laser focus unit with a means for moving a workpiece around with respect to the laser beam. From the advent of robots in the industrial workplace, robots have advanced from being utilized as merely loaders, or part manipulators, to the present state-of-the-art where the robot actually becomes a full process machine having as many as six axes of movement due to advanced wrist designs. These full process robots, are capable of performing many operations, such as precision measurement of a workpiece.
Recently, it has been suggested that the end effector of a robot wrist might be utilized to carry a laser focus unit so that complex operations could be performed on a workpiece through use of a "wieldable" laser, that is, capable of movement through a high degree of multispatial orientations. Many power lasers operate in the infrared or invisible light spectrum, so that personnel may not be able to visually detect the presence or absence of a laser beam such as that emitted by a carbon dioxide laser. Several formidable problems arise when using a wieldable laser, particularly that which emits radiation in the infrared spectrum: (1) The laser beam may be directed at surfaces other than in the work zone by improper focusing on the target; or (2) the laser beam, which is reflectable radiation, may strike a reflective surface and be redirected to a point outside the work zone. As a result of these problems, injury to personnel and damage to environmental points outside the work zone may occur. It has been known in the robot industry, at least on an experimental basis, that a single layer of shielding material might be employed around a laser work zone, to protect the environment from a stray laser beam. Ideal shielding materials should be capable of absorbing at least a portion of the laser beam energy.
The carbon dioxide laser is probably the most widely used and versatile type of power laser in use. It can emit infrared radiation at many discrete wave lengths between nine and eleven micrometers. While carbon dioxide gas is the light emitter, CO.sub.2 lasers usually contain a mixture of other gases together with carbon dioxide to accomplish the lasing of light. The internal workings of CO.sub.2 (and other types) power lasers is generally of no concern to the shielding designer, provided that the wave length of the emitted light is known for shielding purposes. It is known that ordinary glass will totally absorb 10.6 micrometer energy and, in fact, can be cut with CO.sub.2 lasers. Conversely, many optical materials are transparent at 10 micrometers but do not transmit visible light very well. It is preferable in many cases to have shield which is transparent to the human eye so that the work zone may be viewed while the operation is being performed.
Single shielding layers of a thermoplastic material such as transparent acrylic, commonly available under the trademarks LEXAN and PLEXIGLAS have been successfully employed for shielding a power laser beam, because the material will absorb at least a portion of the laser beam and will degrade accordingly. For example, a power laser beam in the range of lkw will take approximately 15 seconds to burn through a 1/4 inch thickness acrylic plastic. Personnel in laboratory situations can readily detect the discoloration occurring on a portion of a plastic shield, and generally have sufficient time to shut down the system and find the fault in misdirection of the laser beam. Obviously such a scheme depends totally on manual intervention.
Applicant has obviated many difficulties inherent in the laboratory attempts to shield a laser beam work zone and visibly detect a stray laser beam, by designing an automatic device which will, upon continued presence of a stray laser beam, provide a signal which is indicative of the fault condition, and which is capable of automatically initiating a machine shut down condition.
It is therefore an object of the present invention to provide an automatic sensing system for shielding a laser work zone.
Another object of the present invention is to provide a signaling device to indicate a laser direction fault condition.
Still another object of the present invention is to provide a shielding device for a laser work zone which is capable of sensing and signaling a laser fault condition, wherein the signal may be utilized for a variety of purposes, including actuating an alarm such as an annunciator or visual device for machine personnel, and for initiating a shut down of the lasing apparatus.